Many classes of antibacterial agents are known, including the penicillins and cephalosporins, tetracyclines, sulfonamides, monobactams, fluoroquinolones and quinolones, aminoglycosides, glycopeptides, macrolides, polymyxins, lincosamides, trimethoprim and chloramphenicol. The fundamental mechanisms of action of these antibacterial classes vary.
Bacterial resistance to many known antibacterials is a growing problem. Accordingly there is a continuing need in the art for alternative antibacterial agents, especially those that have mechanisms of action fundamentally different from the known classes.
Amongst the Gram-positive pathogens, such as staphylococci, streptococci, mycobacteria and enterococci, resistant strains have evolved/arisen which make them particularly difficult to eradicate. Examples of such strains are methicillin resistant Staphylococcus aureus (MRSA), methicillin-resistant coagulase negative staphylococci (MRCNS), penicillin resistant Streptococcus pneumoniae and multiply resistant Enterococcus faecium. In view of the rapid emergence of multidrug-resistant bacteria, the development of antibacterial agents with novel mechanisms of action that are effective against the growing number of resistant bacteria, particularly the vancomycin resistant enterococci and beta-lactam antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus, is of utmost importance.
Cell division has been of considerable interest to the pharmaceutical industry as a target because it comprises a group of well conserved target proteins that are all essential for the viability of a wide range of bacteria, and their activities are completely different from those of the proteins involved in cell division of mammalian cells. A number of compounds that act on components of the cell division machinery have been described (Ohashi, Y. et al. J. Bacteriol. 181, 1348-1351 (1999),
Jennings, L. D. et al. Bioorg. Med. Chem. 12, 5115-5131 (2004), Sutherland, A. G. et al. Org Biomol Chem 1, 4138-4140 (2003), Margalit, D. N. et al. Proc. Natl. Acad. Sci. USA 101, 11821-11826 (2004), Wang, J. et al. J. Biol. Chem. 278, 44424-44428 (2003), White, E. L. et al. J. Antimicrob. Chemother. 50, 111-114 (2002), Reynolds, R. C. et al. Bioorg. Med. Chem. Lett. 14, 3161-3164 (2004) and Stokes et al. J. Biol. Chem. 280, 39709-39715 (2005)). So far, most effort has been directed at the FtsZ protein, since it has several biochemical activities that can be assayed in vitro. Unfortunately, most of the compounds described so far either have relatively low potency, undesirable pharmacological properties or unknown specificity.